In a wide range of applications, it is desired to elevate a liquid from a lower reservoir to a higher or upper reservoir which is vertically above the lower reservoir. One example of such application is an elevated reservoir for fish cultivation, where fresh water is supplied from a lower reservoir to the elevated reservoir and old water is drained from the elevated reservoir back to the lower reservoir. Further applications include cooling installations for power production, process industry, oil rigs, ships and similar.
US 2014/299196 A1 discloses a water lifting system, in particular a fire extinguishing system for offshore installations, comprising a pump-turbine assembly with a pump unit and a turbine unit. The pump unit has an intake port below the sea level and and a discharge port connected to a pump via a first line. A second line leads from the pump to a first distribution device on the offshore installation. A fourth line connects the first distribution device to the turbine unit.
The water lifting system in US 2014/299196 A1 has a complicated and expensive design. Moreover, the system causes high losses and the efficiency is consequently low.